Touch pads and touch screens responsive to localized depression pressure have been provided to create "buttons" for data input. A touch pad device is disclosed, for example, in U.S. Pat. No. 3,911,215; and, a transparent touch screen for overlayment and use with the display screen of a cathode ray tube is disclosed, for example, in U.S. Pat. No. 4,220,815, the disclosures of both of these patents being incorporated by reference herein.
These previously patented devices rely upon resistive sheets in which uniform orthogonal electric fields are generated in two-phase sequences, for example, as shown in FIG. 1 of the referenced '215 patent. When a low resistance or ground connection is established at a particular location on the sheet, as by depressing an overlying, low resistance ground or signal return sheet into electrical contact with the resistive sheet, precise orthogonal field (x,y) pinpointing of the location of depression may be provided. Thus, these prior devices have been utilized in conjunction with a computer system to create "push-buttons". When a particular push-button (i.e. location on the resistive sheet) is depressed ("touch"), or released ("untouch"), the computer has sensed this occurrence and has responded operationally thereto.
Other technologies have been applied to create touch screens and pads, including surface accoustic wave technology; and these screens and pads have also been used with computing systems to create push-buttons. The surface accoustic wave touch screen has the additional capability of reporting a z-coordinate indicative of the velocity or force with which the screen or pad is touched.
Traditionally, touch screens or pads have accomplished push-button sensing either through a touch, i.e. when the operator's finger or a stylus first touches the screen; or, an untouch, i.e. when the finger or stylus is released from the screen or pad. "Touch" is the most natural action for a novice user, because it represents activation on contact, just like the expected action of a conventional electromechanical push-button. For example, with a touch screen implementation, a user touches a labelled, delineated area on the screen, and a resulting action and acknowledgement are then given e.g. by an appropriate display on the screen.
For "untouch", the touch step (which of course must come first) usually initiates some form of visual feedback, such as highlighting a screen area or option. The area or option is not actually selected to perform its action until the user "untouches" the screen. Thus, with "untouch" the slightly more experienced user can move finger or stylus on the screen to be sure the proper area is highlighted and then untouch or remove finger or stylus in order to complete the selection process. This approach enables a far greater precision in selection of desired areas on the screen.
The "touch" and "untouch" procedures are satisfactory for many applications, but they have significant shortcomings. Often it is very desirable or necessary to display the visual feedback following a user's finger around the screen while not forcing the user actually to make a selection upon the untouch action. To achieve this feedback using normal touch screen operations, it is necessary to completely divorce the untouch action from selection. An operation with visual feedback is first used to determine a position on the screen, but the untouch action does not cause a selection to be made. A second touch/untouch operation is then required on the screen (or via some other input device such as a keyboard) in order to perform the select operation.
This prior requirement for two disparate actions to perform a single selection is not satisfactory. In order to accomodate the occasional time when an untouch action will not lead to a selection, the user's attention must be diverted for each such action. This inconvenience becomes intolerable when dealing with a sequence of operations as typically encountered in computer aided design (CAD) or even in simple word processing applications. One way of further illustration of this inconvenience is by drawing an analogy to a hypothetical typewriter which would require the typist to strike a ribbon advance key after each symbol key was struck merely to advance the ribbon during typing, a function automatically performed by conventional typewriters.
This inconvenience in prior art touch screens and touch pads has not been experienced with other position-reporting devices, such as computer "mice", "tablets", and "light pens" which usually have actual push-buttons present on the mechanism manipulated by the user's hand during operations. Thus, the user is able to manipulate a computer mouse to a desired orthogonal (x,y) position typically followed by a visual cursor on the display screen and then to actuate one of a plurality of switches on the mouse to initiate or discontinue a particular function.
Thus, a hitherto unsolved need has arisen for the provision of a "virtual" push button for use with touch screens or touch pads which functionally extends the capability thereof to match the capability of other position reporting devices, such as computer "mice", "tablets", and "light pens" which usually have electromechanical push-buttons present on the mechanism for manipulation by the user's hand during positioning operations thereof.